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International audience; In this work, an Artificial Magnetic Conductor (AMC) metasurface composed by a Sierpinski Carpet fractal unit cell is analyzed using the Generalized Boundary Conditions (GBCs). Since the fractal structure cannot be represented using analytical expressions, the detailed GBCs model is presented to analyze angular and polarization stabilities of the obtained metasurface. The angular stability of the fractal geometry is compared with the square loop and Jerusalem Cross geometries, from the stable bandwidth and frequency deviation. Finally, the computational effort and the accuracy of the proposed method is compared to conventional methods through performance parameters, thus validating GBCs as an alternative method to characterize AMCs.

The knowledge of the electromagnetic constitutive properties of materials is crucial in many applications. Free-space methods are widely used for this purpose, despite their inherent practical difficulties. This paper describes an affordable free-space experimental setup for the characterization of flat samples in 1&ndash, 6 GHz in a non-anechoic environment. The extracted properties are obtained from the calibrated Scattering Parameters, using a frequency-by-frequency solution or a multi-frequency reconstruction. For the first, we describe how the Time-Domain Gating can be implemented and used for filtering the signals. For the latter, a weighting factor is introduced to balance the reflection and transmission data, allowing one to have a more favorable configuration. The different role of transmission and reflection measurements on the achievable results is analyzed with regard to experimental uncertainties and different noise scenarios. Results from the two strategies are analyzed and compared. Good agreement between simulation, measurement and literature is obtained. According to the reported results for dielectric materials, there is no need of filtering the data by a Time-Domain Gating in case of the multi-frequency approach. Experimental results for Polymethylmethacrylate (PMMA) and Polytetrafluorethylene (PTFE) samples validate both the setup and the processing.